A Universal Mobile Telecommunication System (UMTS) is a broadband, packet based system for the transmission of text, digitized voice, video and multi-media. In a UMTS based network (or UTRAN, where UTRA stands for UMTS Terrestrial Radio Access), a Radio Resource Control (RRC) part of the protocol stack is responsible for the assignment, configuration and release of radio resources between the UE and the UTRAN. Two basic modes that the UE can operate are defined as “idle mode” and “UTRA RRC connected mode” (or simply “connected mode”). In idle mode, the UE is required to request a RRC connection from the UTRAN whenever it wants to send any user data or respond to a page for receiving data from an external data network such as a push server. When in a RRC connected mode, the UE can be in one of four states:
CELL-DCH: a dedicated channel is allocated to the UE in the uplink and downlink directions in this state to exchange data;
CELL_FACH: no dedicated channel is allocated to the UE in this state; instead, common channels are used to exchange a small amount of bursty data;
CELL_PCH: the UE uses Discontinuous Reception (DRX) to monitor broadcast messages and pages through a Paging Indicator Channel (PICH) and no uplink activity is possible; and
URA_PCH: this state is similar to CELL_PCH, except that a UTRAN Registration Area (URA) UPDATE procedure is only triggered through URA reselection.
In the IDLE state, when the UE requests an RRC connection, the network (NW) decides whether to move the UE to the CELL_DCH or CELL_FACH state. Conversely, when the UE is in an RRC connected mode, the network can decide when to release the RRC connection. The network may move the UE from one RRC state to another before releasing the connection or instead of releasing the connection. The state transitions are typically triggered by data activity or inactivity between the UE and network. Since the network may not know when the UE has completed a data exchange for a given application, the network maintains the RRC connection for a pre-determined time period in anticipation of more data exchange with the UE. Maintaining the connection can reduce latency due to re-establishing a previously released connection that can require a call set-up and radio resource allocation. An RRC connection release message can be sent by the UTRAN to release the signal link connection and all radio resources between the UE and the UTRAN. The RRC connection release message can be sent in response to a Signaling Connection Release Indicator (SCRI) message sent to the network by the UE after a pre-determined period of inactivity. The length of time to wait before sending the message can be fixed by the network.
Sending the SCRI message to the network based on a fixed timer can be not optimized for variable rates of packet transmission between the UE and the network. The pre-determined period of inactivity set by the network can be not matched well to the frequency of data transmission to and from the UE, which can vary significantly for different applications. Sending the SCRI frequently can provide rapid release of radio resources benefiting the network and can conserve battery power at the UE; however, re-establishing an RRC connection can require additional signaling exchanges between the UE and the network. Sending the SCRI infrequently can provide an extended connection between the UE and the network; however, limited power storage at the UE can be drained unnecessarily during periods of data transmission inactivity, and radio resources can be assigned to the UE that could be used to other mobile devices served by the same UTRAN of the wireless network.
Therefore, a need exists for a method, apparatus, and system for adapting a time for releasing connections between a wireless mobile communication device and a wireless network to balance power consumption, radio resource allocation and signaling frequency.